My Quad's Audio-out minijack in the rear pops randomly with a few second intervals and I haven't been able to solve the issue.
Things done this far: Added a ground loop isolator to the audio cable as suggested in the Apple kbase document, and had an electrician check out that my outlets are properly grounded. No Help.
The front minijack doesn't pop, but if I connect my active speakers to it, I can hear the infamous chirp sound for example when using exposé. The chirps can't be heard from the rear minijack.
The audio-out still pops for a while even if I shut down my computer and disconnect all cables except the speaker cable. Yes, also the power cord is disconnected and my Quad still pops.
The remaining electricity in the power supply seems to leak to the audio-out port and cause these pops. My speakers are OK, they don't pop when connected to anywhere else than my Quad.
The popping starts when the computer has been on for several hours. Disconnecting the power and speaker cables seems to help for a few minutes until the popping starts again.
The computer is connected to an UPS. It doesn't make a difference if I connect the speakers to the UPS also.